Decreasing lead bioaccessibility in industrial and firing range soils with phosphate-based amendments.
In-situ stabilization using phosphate (P) amendments, such as P-based fertilizers and rock, are a potentially cost-effective and minimally disruptive alternative for stabilizing Pb in soils. We examined the effect of time (0-365 d), in vitro extraction pH (1.5 vs. 2.3), and dosage of three P-based amendments on the bioaccessibility (as a surrogate for oral bioavailability) of Pb in 10 soils from U.S. Department of Defense facilities. Initial untreated soil bioaccessibility consistently exceeded the U.S. Environmental Protection Agency default value of 60% relative bioavailability, with higher bioaccessibility consistently observed at an in vitro extraction pH of 1.5 vs. 2.3. Although P-based amendments statistically (P < 0.05) reduced bioaccessibility in many instances, with reductions dependent on the amendment and dosage, large amendment dosages (approximately 20-25% by mass to yield 5% P by mass) were required to reduce average bioaccessibility by approximately 25%. For most amendment combinations, reductions continued to occur for periods up to 1 yr, indicating that the observed reductions were not merely experimental artifacts of the in vitro extraction procedure. Although our results indicated that reductions in Pb bioaccessibility with P amendments are technically feasible, relatively large amendment masses were required to achieve relatively modest reductions in bioaccessibility. The cost and potential environmental implications of adding such large amounts of P may limit the practicality of in situ immobilization for some Pb-contaminated soils, industrial and firing range soils in particular.
Moseley
Rebecca A
RA
Dep. of Civil Engineering, 208 Harbert Engineering Ctr., Auburn Univ., Auburn, AL 36849, USA.
Barnett
Mark O
MO
Stewart
Melanie A
MA
Mehlhorn
Tonia L
TL
Jardine
Philip M
PM
Ginder-Vogel
Matthew
M
Fendorf
Scott
S
D005389:Firearms; D007220:Industrial Waste; D007221:Industry; D007854:Lead / Q000737:chemistry* / Q000378:metabolism*; D010710:Phosphates / Q000737:chemistry*; D012987:Soil / Q000032:analysis*; D012989:Soil Pollutants / Q000737:chemistry* / Q000378:metabolism*
D007220:Industrial Waste; D010710:Phosphates; D012987:Soil; D012989:Soil Pollutants; D007854:Lead